Gear-tooth rotary pump



Nov. 21, 1950 w. w. HAMILL GEAR-TOOTH ROTARY PUMP Filed Jan. 25, 1946INVENTOR Patented Nov. 21, 1950 GEAR-TOOTH ROTARY PUMP William WilsonHamill, Little Aston, England Application January 25, 1946, Serial No.643,251 In Great Britain January 31, 1945 1 Claim. 1

This invention relates to rotary pumps of the gear tooth type and moreparticularly to those intended to deal with liquid carrying 0rcontaminated with foreign substances such as sand, grit, earth, etc.which in pumps of conventional design, quickly wear out the meshingparts.

The object of the present invention is a geartooth pump which reducesabrasive action on the meshing surfaces; which therefore increases theeffective life of such surfaces; in which the high pressure zone is moreeffectively isolated from the low pressure zone; and which betteraccommodates foreign bodies present in the liquid.

Reference may be had to the accompanying drawings in which Figure 1 is asectional elevation, and Figure 2 a sectional end elevation at rightangles to Figure 1, of a pump according to the invention.

Figure 3 is a fragmentary view of a modification.

In the drawings there is shown a pump having one set of gears fortransmission of rotary motion, and a second set of gears driven therebyadapted for pumping action. Conveniently the pump housing I includes twochambers 2, 3 separated by a partition, one chamber containing thedriving gears or wheels 4 of normal tooth type and the other the pumpinggears or wheels 5.

Either or both the pumping wheels may include elastic provision adaptedto effect a sealing action at the roots and tops of the pumping teeth intheir traverse of the meshing zone, which provision preferably takes theform of tooth forms either hollow or solid made of rubber or materialhaving like properties or characteristics. The flank contour has not theimportance of conventional tooth pumps since there is not or need not besubstantial pressure between meshing flanks, light contact or follow-uppressure being sufiicient to provide the seal between contacting flanks.To provide sealing action at the tooth tops and the roots of the toothspaces, the radial length of a tooth exceeds the radial length or depthof a tooth space by a suitable amount so that when the teeth are fullymeshed and to a limited angular dimension each side thereof, thereresults a displacement or deformation of the rubber in the region of thetooth tops and bottoms of the tooth spaces with consequential radialpressure in addition which produces an effective seal against passage orescape of liquid from the high pressure side to the low pressure side,excess rubber volume being displaced into the parts of the tooth spacesnot occupied by the co-acting teeth.

The yielding character of the teeth allows foreign substances to becarried through the meshing zone without damage to the teeth. The twopumping wheels act solely as followers since driving torque is confinedto the driving wheels.

Special shapes of teeth are often adopted with the object of avoidingundesirably high stresses by virtually incompressible liquids beingtrapped in closed. contracting spaces, such shapes being themselvesundesirable for other considerations. By the present invention, thetooth forms may be such as to avoid the concomitant restrictions anddrawbacks of both said contours.

The pumping wheels may be wholly of rubber including the hub and theteeth but the preferred form is illustrated in the drawings wherein theelastic or resilient material is embodied in the form of an envelope 6for each wheel as depicted in Figures 1 and 2 or for one wheel only asshown in Figure 3, shaped to follow the contour or cross-section of theteeth and held in place by engagement with tooth stubs I extendingoutwards spoke-wise from the wheel hub; in Figure 3 each stub has a heador enlargement 8 at the end remote from the wheel axis to provide apositive retaining means in co-operation with a correspondingly enlargedcavity in the envelope. The envelope is readily assembled on the wheelwhich is fabricated of relatively rigid material e. g. metal, plasticsby endwise sliding on to the tooth stubs.

At their lateral ends, the teeth of the envelope abut against end discs9 which take the wear from contact with the adjacent end faces of thehousing and are preferably of harder material. Such discs may beprovided with sealing grooves Ill in their end faces.

To ensure correct meshing of the pumping teeth and spaces and properrelation to the driving wheels, it is preferred to manufacture thepumping wheels with splines, keys, or other registering devices formedin the wheel bores and shafts for co-engagement, the teeth being inproper angular relationship with the registering devices. Assembly andreplacement are thereby facilitated since the parts are arranged so thatthere is only one angular position for each wheel in which it can bemounted.

Where abrasive substances are present in the liquid, it is preferred toprovide both wheels with the elastic or resilient provision to avoid apossible lapping action, but in suitable application, one

.- wheel only may be so constructed.

Having thus described my invention, what I claim is:

A gear tooth rotary pump comprising a pump chamber having an inlet andan outlet, meshing pump gears in said chamber, means for driving saidgears, and an elastic covering on the teeth of at least one of saidgears, said gear teeth having reduced shank portions and "enlarged endportions and the respective covers therefor each having a socket tocooperate with the shape of its respective tooth to retain said coveringin position. 1 7

WILLIAM WILSON HAMILL.

REFERENCES CITED The following references are of record "in the file ofthis patent:

Number 4 UNITED STATES PATENTS Name Date Clow July 8, 1856 Bazin June25, 1867 Schmidt July 29, 1930 Hill June 14, 1932 Morton June 1, 1937QI-Ia'wley 'Apr. 2, 1940 Fraser June '17, 1941 Sibley July 28, 1942Hoopes Aug. 21, 1945 Hanna July 9, 1946 Wallgren Sept. 17, 1946

